Percussive tool



March 13, 1951 M. A. sTUTz 2,545,245

PERCUSSIVE TOOL Filed April 8, 1948 2 sheefnLs-hee*v lV Patented Mar. 13, A1951l PERCUSSIVE TOOL Max Arnold Stutz, London, England Application April 8, 1948, Serial No. 19,830

- in Great Britain April 18, 1947 `11 Claims. (C1. 12s- 33) This invention has reference to improvements in or relating to percussive or vibrating apparatus such as power hammers and the like of the kind wherein a striker body or tup which delivers blows to a transmitter is reciprocated by the centrifugal action of two rotatable outer masses, interconnected so as to rotate similarly and simultaneously, and of an inner mass rotatable in the opposite sense to and located between said outer masses, the masses having a common axis of rotation.

The striker or tup is arranged to deliver blows to a transmitter, such as a socket, adapted to be connected to the working implement (a drill, chisel, spade, riveting head or other suitable tool) or to be connected to a body to be vibrated, e. g., a mould for concrete.

In this type of apparatus the outer masses are substantially balanced centrifugally in relation to the inner mass, all masses rotate at the same rate and the common centre of momentum of the outer masses and the centre of moment of the inner mass are symmetrical with respect to, and substantially in the plane containing the axis of reciprocation of the striker body. Such a balanced arrangement results in the absence of torsional and other unbalanced forces which if present would cause the apparatus to yaw when in use and would tend to cause the driving motor of the apparatus periodically to stall.

The principal object of the present invention is the provision of an improved construction of apparatus of the above type wherein the two outer masses rotating in the same direction and the inner mass rotating in the opposite direction are driven by but two gear wheels and a kgear meshing with said wheels whereby frictional losses are reduced to a minimum.

Another object of the invention is the provision of a percussive tool wherein shocks on the drive gearing and driving motor every time the striker hits the transmitter are cushioned. This permits of the use of heavier masses and/or higher speeds in comparison with tools at present in use, compared input for input, and, therefore l and a driving bevel gear in mesh with both bevel wheels, one of said bevel wheels being in driving relation to the outer masses and the other bevel wheel being in driving relation to the inner mass.

The axis of rotation of the driving bevel gear is preferably substantially co-incident with the axis of reciprocation of the striker body.

In order to lessen shock on the bevel gearing and the possibility of the motor stalling every time the striker hits the transmitter, the couplings between the said wheels and their associated masses are of resilient or shock absorbing form, said couplings being so constructed as to limit the degree of relative rotation between the gear Wheels and their respective masses in order to prevent the outer masses and the inner mass from becoming unbalanced relatively.

One example of construction of percussive tool according to the invention willfnow be described with reference to the accompanying drawings wherein:

Fig. 1 is a part sectional elevation of the tool, the plane of section being the mid-plane thereof;

Fig. 2 is 'a sectional plan view on the plane indicated by the line II-II, Fig. 1; and

Fig. 3 is a detail, in side elevation, concerned vwith the drive transmission to the rotating masses.

The upper part of the tool may be of substantially conventional form so, therefore, will not need a detailed description. An electric motor, a pneumatcmotor or the like in the case I drives a tube 2 which makes driving engagement with the splines on a drive-shaft 3, said shaft being slidable or telescopic in relation to the tube 2.

The rotating, eccentric fly weights are indicated at 4, 4 and 5. The weights or masses 4, 4 are on sleeves 6 which are directed towards each other and are coupled together by dogs 1 at their adjacent ends. A bush 8 located centrally of a bevel wheel 9 with which it is rigid surrounds the sleeves 6 between the masses 4, 4 and a bush I0 located centrally of a similar bevel wheel I I and rigid therewith surrounds the bush 8, the bevel wheel 9 being at Vone side of the weight or mass 5 and the bevel wheel II being at the other side thereof and said bevel wheels being vset to mesh with a single bevel pinion I2 at' the bottom of the shaft 3.

From the above it will be evident that the masses 4, 4 are connected together by a shaft (the intercoupled sleeves 6) which lie within the orbit of the mass 5 and is co-axial with the axis ofrotation of the said mass. This enables one bevel wheel, the bevel wheels, as will be explained, to rotate both masses 4, 4 simultaneously in the same direction, and the bevel wheel II rotates the mass 5 in the opposite direction, when the two wheels are driven in opposite directions by the pinion I2.

The masses 4, 4, are rotatably mounted on a cross shaft I3 supported at its ends by bearings I4 in a reoiprocable striker body or frame I5; the bush 3 of the bevel wheel 9 is supported by the sleeves 6 and the bush II] of the wheel Il is supported by the bush 8, whilst the mass 5 is supported by the bush I0.

The frame terminates at its top and bottom in collars II and I'I, respectively. The collar I6 makes sliding engagement with a hollow spigot I8 depending from a mounting plate I9 at the bottom of the motor case I and the collar I1 makes sliding engagement with an upwardlly extending spigot rigid with the bottom of a case 2| enclosing the components 4 to 20, said case being xed to the case I in any suitable manner.

Either spigot or both spigots and the corresponding collar may have a flat or ats to prevent rotation of the frame I5 on the spigots. For example, the spigot I8 and the collar` I6 may be square as shown in Fig. 2.

It will now be evident that when the masses are rotated forces which act vertically down wards when the masses are descending will urge the frame I5 downwards and forces which act vertically upwards when the masses are ascending will urge the frame upwards. Hence, the frame will reciprocate on the spigots I8 and 20. This principle is, of course, known. In the present tool the mass of all the moving parts in the case 2l is substantially balanced with respect to the axis of reciprocation x-.n That is to say, the frame I5 and the collars on it are substantially symmetrical with respect to the said axis, the axis of the drive shaft and pinion I2 coincides therewith and the centre of momentum of the mass 5 and the joint centre momentum of the masses 4, 4 are in the planeA containing this axis parallel to the planes of rotation of the masses. As a result of this arrangement there are substantially no unbalanced forces tending to rotate the tool or otherwise to cause it to yaw. Moreover; as there are no substantial torsional forces produced there is no tendency of the motor to stall from this cause, stalling occurring in the known, unbalanced tools when .the torsional forces act in opposition to the motor drive.

Balancing of the masses 4, 4 in relation to the mass 5, and the location of the axisof the shaft 3 in their axis of reciprocation, is made possible by the drive transmission formed by the sleeves 6 coupling the masses 4, 4 together, the bevel wheels and the inner mass 5 being rotatable around the said sleeves.

A' striker head 22 is secured to the bottom of the frame I5 and operates ona transmitter or tool holder 23, the transmitter being slidably supported in a bearing 24 at the bottom of the case 2! and the axis of said transmitter being in the axis of reciprocation of the frame. The usual leather or rubber gaiter is indicated at 25.

Another advantage of the tool shown in the drawings, therefore, is that `because the striker assembly, namely the frame I5 and the parts carried thereby, is supported at its top and bottom jamming of the assembly is avoided.

I The bevel Wheels 9 and II drive the masses, as previously stated. In order to safeguard the bevel gearing .and tofprevent vthe motor `from stalling every time the striker head hits the transmitter, and as a result to permit of full advantage being taken of the symmetrical arrangement of the parts enabling heavier masses to be used and/or the rate of rotation of the masses to be increased, the bevel wheels are connected to their respective masses by a resilient or shock absorbing drive transmission, said transmission, moreover, limiting the degree of relative motion between the bevel wheels and their masses whereby the oppositely rotating masses cannot get out of balance, and also ensuring that energy absorbed by the resilient elements is mainly passed to the masses in the form of useful work.

In the present tool each bevel wheel is associated with a flexible drive transmission. Each transmission shown comprises coil springs 26 and 2'I in complementary grooves 28, of arcuate form, in the sides of the bevel wheels and the adjacent sides of the masses to which the wheels have to be coupled., One end of each spring is secured to a block 3b attached to a bevelwheel, and the opposite ends of the springs are secured to blocks 32 at the opposite ends of the grooves in the masses. For one direction of rotation of the drive shaft the springs 26 will be transmite ting springs and the springs 21 will be reaction springs; and vice versa for the opposite direction of rotation of the shaft. Relative rotary movement between the gear wheels and their respecs tive masses is limited by the blocks 32 fixed in the ends of the grooves 28. in the masses.

The frame I5 and the components mounted on it are normally suspended by the coil spring 33, which isalso a cushioning spring, within the collar I'I and spigot 2li, said spring surrounding the upper end of the transmitter. A reaction spring 34 is located within the collar I6 and the spigot I8, this spring surrounding the drive shaft and the bearing 35 therefor, which bearing is at the top part of the frame and is, of course, co-axal with the axis of the reciprocation of the frame.

The principal advantages of a tool constructed according to the invention may be summarised as follows: Owing to the construction permitting the outer masses and the inner mass to be driven by only three bevel gears, gear losses are reduced to a minimum and the symmetrical construction of the striker assembly with respect to the axis of reciprocation is facilitated, the resulting absence of substantial torsional forces and other unbalanced forces tending to cause the tool to yaw and to cause the motor to stall permitting of the use of heavier massesv and or greater rates of rotation of the masses in comparison with known tools of the same power input, tools according to the invention being more powerful and more ecient therefore; and owing to the resilient drive transmission between the bevel wheels and their respective masses such heavier masses and/or greater speeds of rotation -may be used Without a corresponding rise in the possibility of damaging the bevel gearing or of causing the motor to stall when the striker hits the transmitter. Other advantages include the regaining of the energy absorbed by the resilient drive transmission when the striker hits the transmitter, and the absence of jamming-by the striker.

What I claim is:

l. A percussive apparatus comprising a reciprocably mounted striker, two outer centrifugal masses rotatably mounted on said striker, an inner centrifugal mass rotatably mounted on said striker. the axes of rotation or the masses being co-incident, connecting means between the outer masses positively connecting them together, said connecting means being located inside the orbit of said inner mass, and toothed gearing for rotating said mass, said toothed gearing comprising but three wheels, namely, a rst gear wheel coupled to one outer mass, a second gear wheel coupled to the inner mass and a driving gear in mesh with said first and second gear wheels, said driving gear having its axis at right angles to the axes of said rst and second gear wheels, the said connecting means and toothed gearing cooperating to rotate the outer centrifugal masses simultaneously in one direction and the inner centrifugal mass in the opposite direction.

2. A percussive apparatus according to claim 1, the axis of rotation of the driving gear being substantially zzo-incident with the axis of reciprocation of the striker body.

3. A percussive apparatus according to claim l, the axis of rotation of the driving gear being substantially 3o-incident with the axis of reciprocation of the striker body, the assembly comprising the striker body, the masses mounted on said body and the first and second gear wheels, being substantially symmetrical with respect to the said axis of reciprocation.

4. A percussive apparatus according to claim 1, comprising a drive coupling of resilient construction between said first gear wheel and its associated mass and a drive coupling of resilient construction between said second gear wheel and its associated mass, and means for limiting the degree of relative rotation between each gear wheel and its associated mass.

5. A percussive apparatus according to claim 1, comprising a cross shaft mounted on the striker, said connecting means being of sleeve like form and surrounding said cross shaft, and said inner mass being rotatably mounted around saidsleeve-like connecting means.

6. A percussive apparatus according to claim 1, comprising a cross shaft mounted on the striker, said connecting means being of sleeve-like form and surrounding said cross shaft, said rst gear wheel having a boss, said iirst gear wheel and said boss being rotatably mounted on said sleeve-like connecting means, said second gear wheel having a boss, said second gear wheel and the boss thereof being rotatably mounted on the boss of said first gear wheel, said inner mass being locatedbetween said gear wheels and being rotatably mounted around the boss of said second gear wheel, a resilient drive coupling between said rst gear wheel and one of said outer masses, and a resilient drive coupling between said second gear wheel and said inner mass, each of said drive couplings having means for limiting the degree of relative rotary movement betweenv its associated gear wheel and the mass associated with the said Sear wheel.

'7. A percussive apparatus according to claim 1, comprising a support for the striker at one end thereof and a support for the striker at the opposite end thereof, and means for holding the striker body against rotation on said supports.

8. A percussive apparatus according to claim 1, comprising a support for the striker at one end thereof and a support for the striker at the opposite end thereof, and means for holding the striker body against rotation on said supports, said supports being of collar and spigot form.

9. A percussive apparatus according to claim 1, comprising a suspension and cushioning spring at the bottom of the striker and a reaction spring at the top of said striker.

10. A percussive apparatus comprising a case, a transmitter mounted at one end of said case, a driving motor at the opposite end of said case, a striker frame within said case, a collar andA spigot support at one end of the case and a collar and spigot support at the opposite end of said case, said supports reciprocably bearing said striker frame, a cross shaft mounted in said striker frame, two centrifugal outer masses mounted on said cross shaft in relatively spaced relationto each other, a sleeve around said cross shaft positively` coupling said masses together, a rst gear wheel coupled to one of said masses, an inner mass rotatably mounted around said sleeve, a second gear wheel coupled to said inner mass, a driving gear wheel in mesh with said rst and second gear wheels, said driving gear wheel being mounted in said frame and having its axis in the axis of reciprocation of said frame, and a telescopic drive coupling between said motor and said driving gear wheel, the centre of momentum of the inner mass and the joint centre of momentum of the outer masses being substantially in a plane containing the axis of reciprocation of the striker.

11. A percussive apparatus comprising a reciprocably mounted striker, two outer centrifugal masses rotatably mounted on said striker, an inner centrifugal mass rotatably mounted on said striker, the axes of rotation of the masses being co-inoident, connecting means between the outer masses positively connecting them together, said connecting means being located inside the orbit of said inner mass, and toothed gearing for rotating said masses, said toothed gearing comprising but three wheels, namely, a nrst gear wheel coupled to one outer mass, a second gear wheel coupled to the inner mass and a driving gear in mesh with said first and second gear wheels, said first gear wheel being located at one side of said inner mass and said second gear wheel being located at the opposite side of said inner mass and said driving gear having its axis at right angles to the axes of said first .and second gear wheels, the said driving gear, first and second gear wheels and connecting means cooperating to rotate the two outer centrifugal masses simultaneously in one direction and the inner centrifugal mass in the opposite direction.

MAX ARNOLD STUTZ.

REFERENCES CITED rEhe following references are of record in the file of this patent:

UNITED STATES PATENTS 

